J. Agric. Food Chem. 1994, 42, 1355-1357
1355
Effects of Several Commercial Plant Growth Regulator Formulations on Yield and Allelochemicals of Cotton ( Gossypium hirsutum L.) Paul A. Hedin' and Jack C. McCarty, Jr. Crop Science Research Laboratory, Agricultural Research Service, U.S. Department of Agriculture, Mississippi State, Mississippi 39762-5367
In recent years, a number of kinetin-based commercial plant growth regulators have been evaluated for their effects on various crop plants. In a study a t Mississippi State during 19861992,five commercial plant growth regulators and urea were evaluated as foliar sprays on growing cotton (Gossypium hirsutum L.) plants for their effects on yield, agronomic traits, and pest allelochemicals. Of the five tested, the activities of three (Burst, Foliar Triggrr, and Maxon) were attributed by their providers to cytokinins. FPG-5 contained cytokinins, IAA, GA, and several inorganic micronutrients, and PG-IV contained IBA, GA, and micronutrients, but no cytokinins. FPG-5 and Foliar Triggrr caused statistically significant increases in yield, but only in 1992. The foliar application of urea had a consistently negative effect on yield. Formulations containing IAA/IBA, GA, and inorganic micronutrients did not appear to cause more positive yield trends than those whose potencies were attributed to their cytokinin content. Positive trends in bud gossypol were observed upon treatment with Burst, Foliar Triggrr, and PG-IV.
INTRODUCTION
field tests showed that kinetin and two commercial kinetin formulations tended to increase yield of cotton, pest resistance, and four allelochemicals: gossypol, condensed tannins, flavonoids, and anthocyanins (Hedin et al., 1984, 1988a,b;McCarty et al., 1987;McCarty and Hedin, 1989). These allelochemicals have been shown to be toxic to the tobacco budworm [Heliothis uirescens (F.)],a major pest of cotton, and therefore could be associated with yield (Hedin et al., l984,1988a,b).
In recent years, a number of kinetin-based commercial plant growth regulator preparations have been evaluated for their effects on yield and agronomic traits of various crop plants. Cytokinins were discovered as a result of efforts to find factors that would stimulate plant cells to divide, and subsequently they were shown to affect various plant processes. The synthetic cytokinin, kinetin, was identified by Miller et al. (1955) as a result of its ability to stimulate cell division. Kinetin is not naturally occurring but results from heat-induced degradation of DNA. The basis for foliar application of cytokinins to field plants is inferred from the improved growth of plants in cytokinincontaining solutions. While in some situations cytokinins may not be active unless other hormones are present, cytokinins alone can nevertheless evoke a variety of physiological, metabolic, biochemical, and developmental processes when applied to plants. A detailed description of the roles of cytokinins in plant growth can be found in a review chapter by Taiz and Zeiger (1991) and in papers by Weaver (1972) and Elliott (1982). Guinn (1986) has reviewed the hormonal relationships in growing cotton (Gossypium hirsutum L.) plants. Cytokinins can either inhibit or promote abscission, depending on time and site of application, and can promote the ability of an organ to compete for metabolites. Guinn (1986) reported that exogenous applications of cytokinins may promote, rather than retard, abscission unless applied directly to the abscission zone. Retained bolls, however, tended to contain more cytokinin. Urea has been used as a foliar application in the nursery trade to darken leaf color and to reduce stress. In some preliminary tests, it appeared to increase the yield of cotton lint (Hedin and McCarty, 1991). The use of bioregulators on cotton has been investigated extensively, and the literature has been cited in several of our previous papers (Hedin et al., l984,1988a,b; McCarty et al., 1987;McCarty and Hedin, 1989;Hedin and McCarty, 1991). The focus of our present study is several commercial kinetin preparations. Preliminary results from several
1986-1992 Bioregulator FieldTests. The commercialcotton cultivars Stoneville 213 (ST-213),Deltapine 50 (DPL-50),and DES-119, well adapted for the study area, were grown each year on the North Farm at Mississippi State University. The cotton was planted about May 1in single-row (0.97 X 12.8 m; W X L) plots. Insects were controlled allseason with fenvalerate (DuPont Agricultural Products,Wilmington,DE) and Cythion (American Cyanamid, Princeton, NJ). The growth regulator formulations were applied at three rates (zero, low, high, see Table I for rates) to plants whose squares were 'match head" in size on about July 10 and July 24. Each compound was handled as a separate randomized complete block experiment with five replications. The timing of applications and rates were in general those recommended by the provider or as tested previously by us (Hedii et al., 1988a,b;Hedin and McCarty, 1991). Normally, two rates, with the second applicationgenerally %foldhigher, were used to improve the likelihood that a response would be elicited. Each compoundor formulation was weighed or measured and dissolved in 5-10 mL of H20. One milliiiter each of Span 80 and Tween 80 was then added. The solutions were made up to 1.25 L with water just before use. They were applied with a COz-pressurized backpack sprayer delivering 203 L/ha at 207 kPa of pressure. For allelochemicals analyses, plant material (terminal leaves and squares) was collected generally 2 and 4 weeks after the application of the chemicals (about July 31 and August 14) and placed in the freezer (-20 "C)until processed. The plots were machine harvested one time for yield determination when cotton was fully open (about September30). Prior to machine harvest, 25 open bolls were hand harvested from each plot, weighed, and ginned to determine boll size, lint percentage, and seed index. Seed index is the weight in grams of 100 fuzzy seeds. The lint percentage determined was used in calculating
* Author to whom correspondence should be addressed.
Procurement of Bioregulators. Of the five commercial bioregulators,the activity of three was attributed to cytokinins.
MATERIALS AND METHODS
lint yields.
This artlcle not subject to U.S. Copyright. Published 1994 by the American Chemlcai Soclety
Hedin and McCarty
1356 J. Agric. Food Chem., Vol. 42, No. 0, 1994
Table 1. Summary of Changes in Yields and Agronomic Traits of Cotton Treated with Selected Commercial Plant Growth Regulators and Ureaec yield change, 7% lint % boll size seed index year cultivar compd control yield, kg ha-l low high low high low high low high +1.7 -0.2 -0.1 Burst 1393 -10.6 ST-213 1986 -1.4 -1.3 1397 -11.6 0.0 0.0 -3.9 -2.9 -7.0 Burst DPL-50 1988 -0.7 -11.1 -0.8 0.0 0.0 -3.9 -2.9 -2.7 1395 Burst av 1988 1989 1990 1990 1991 1991 1992 1992 1990 1991 1991 1992 1992 1992 1990 1990
-4.5 -5.9 +1.2 -4.6 +7.1 +15.5* +0.7
-5.5 -7.0 -5.9 -15.0 +0.9 +4.5 -0.8 +12.6* -2.0
-1.6 +0.4 -0.9 +0.2 +0.4 +0.2 +0.9 +1.2 +0.1
+0.3 +0.2 -0.6 -0.9 +0.1 +0.3
1269 1146 1343 977 1184
-8.6 -2.9 +0.5 +1.5 -2.4
-13.7 -6.7 -10.11 -2.4 -8.2
+0.2 -0.7 -0.1
+0.3
FPG-5 FPG-5 FPG-5
977 927 952
+8.4
Maxon Maxon Maxon
1269 1528 1399
DPL-50 DPL-50 DPL-50 DPL-50 DES-119 DPL-50 DPLdO DES-119 av
Triggrr Triggrr Triggrr Triggrr Triggrr Triggrr Triggrr Triggrr Triggrr
1397 1212 1528 1269 1447 1399 1128 1084 1308
DPLdO DPLdO DES-119 DPL-50 av
PG-IV PG-IV PG-IV PG-IV PG-IV
DPL-50 DES-119 av DPL-50 DPL-50 av
-3.0 0.0
0.0
+0.7
+o.o
-1.8 -1.8
+3.6
+0.9
0.0
0.0
-8.5 0.0 -2.0 -5.3 -4.3 +8.5 -1.9
-6.4 +6.3 0.0 -3.5 +2.1 +6.4
-4.4
-2.0 -1.9 -7.7
+1.1
-1.8
-3.9
+4.2 +1.9 +2.0 -2.0 +1.5
+0.5
-0.6 +0.6
0.0
0.0
0.0 +3.7 +4.0 -4.0 +0.9
+3.3
+8.4 +5.7 +7.1
-0.9 +0.4 -0.3
+0.3 +1.0 +0.6
+2.0 +4.2 +3.1
-4.0 +4.2 +0.1
+2.3 -2.1 +0.1
+6.4 +5.2 +5.8
+0.4
+0.5
+0.5 +0.5
+0.3 +0.4
+2.1 +2.1 +2.1
+4.2 +6.4 +5.3
-1.8
-0.5
+5.5 +5.5
+0.3 +0.9 +1.8 -1.9 1212 -5.0 -9.0 +3.5 +0.9 DPL-50 urea +0.4 +6.4 -2.6 -0.1 +1.1 +6.6 -0.3 +6.4 1528 DPL-50 urea +0.4 +2.0 0.0 -0.1 +2.0 -14.5 1269 DPL-50 urea +1.8 +1.0 +0.1 -5.3 -2.4 0.0 1399 DPL-50 urea -3.9 -3.9 -13.7 -12.5 +0.2 +0.4 1447 DES-119 urea +1.6 +0.5 +1.0 +2.4 -4.7 -7.3 +0.4 +0.3 1371 urea av Values marked with an asterisk were statistically significant. Rates and numbers of applications: Burst, 0.56 X 2 and 1.12 X 2 L ha-l commercial;Triggrr, 0.56 X 2 and 1.68 X 2 L ha-1 commercial, 0.56 X 3 and 1.68 X 3 L ha-l commercial, 1990, one test; PG-IV, 0.14 X 4 and 0.42 x 4 (and) 0.28 X 2 and 0.84 X 2 L ha-l commercial; FPGd,O.56 X 2 and 1.12 X 2 L ha-l commercial; Maxon, 0.28 X 2 and 0.84 X 2 (and) 0.28 x 3 and 0.84 x 3 L ha-1 commerciai, urea, 60 X 2 and 188 X 2,1989 (and) 188 X 2 and 1876 X 2,1990-1991, g ha-l crystalline. Percent change of yield, boll size, and seed index from the specific control that accompanied the test. Lint percent is reported as numerical change. 1989 1990 1990 1991 1991
*
A fourth contained cytokinins and also IAA and GA. The fifth
RESULTS AND DISCUSSION
did not contain cytokinin but did contain IBA and GA. Burst, a mixture of cytokininsincludingzeatin, was obtained from Burst Agritech, Overland Parks, KS. Foliar Triggrr, a commercial preparation with cytokinin (0.012%) as the stated active ingredient, was obtained from Westbridge Chemical Co., San Diego, CA. Maxon, stated to contain cytokinins as the active ingredient, was obtained from Terra International, Blytheville,AR. FPG-5 Foliar, stated to contain the micronutrients Mg (0.5%), Cu (0.05%),Fe (0.10%),B (0.02% ), Mo (O.oO05% ),andCo(O.oO05% and the hormones cytokinin (150-200 ppm) IAA Auxin (300-400 ppm), and gibberellic acid (concentration not stated), was obtained from Baldridge Bio-Research, Inc., Cherry Fork, OH. PG-IV, stated to contain the micronutrients Mg (1.0%), Cu (0.05%), Zu (0.05%1, Fe (0.10%),B (0.02% ), Mo (O.O005% ), and Co (0.0005%) and the hormones indolebutyric acid (0.001%) and gibberellic acid (O.OOl%), was obtained from Microflo, Lakeland, FL. Urea was obtained from J. T. Baker Chemical Co., Phillipsburg, NJ. Analysis of Allelochemicals. Plant tissue (Ca. 25 terminal leaves and 25 squares (buds)] from each replication was collected, freeze-dried, and ground prior to allelochemicalanalysis. Analysis of allelochemicals(gossypol,tannin, anthocyanin, flavonoid)was conducted following the procedures described by Hedin et al. (1988a). In brief, the terpenoid aldehydes were analyzed at 550 nm according to the phloroglucinol procedure, the condensed tannins by analysis of the chromophore at 550 nm produced by boiling with l-butanol-HC1(955), the anthocyanin by measurement of a methanol-water-HCl(79193) extract a t 540 nm, and the flavonoids by measurement of a 70% aqueous acetone extract complexed with diphenylboric acid-ethanolamine a t 440 nm. Statistical Procedures. Data obtained from the various analyses and measurements were subjected to the analysis of variance, and lsd values were calculated using SAS (1985).
Table 1 presents a summary of changes in yields and agronomic traits of cotton treated with several commercial bioregulators and urea from 1986 to 1992. The percent changes are based on yields of controls that accompanied t h e individual tests. Asummary of changes i n the contents of gossypol, tannins, and flavonoids in squares (buds) of t h e treated cottons is given i n Table 2. Experimental conditions (i.e., rates, numbers of applications, cultivars, climate) were varied over t h e several-year period. While this may limit the ability to make rigorous comparisons, obvious efficacy would nevertheless be apparent. Over t h e s t u d y period, the average (overall) yield of controls was 1400 kg ha-l, and the average lint percent, boll size, and seed index were 39.2, 5.3, and 10.1, respectively. T h e average contents of bud allelochemicals of the controls during t h e period were as follows: gossypol, 0.32%; tannins, 11.99%;and flavonoids, 1.78%. The only compounds whose application caused a statistically significantly increase in yield were Triggrr (15.5%)and FPG-5 (8.4%),both in 1992. However, the t r e a t m e n t with Triggrr did n o t result i n a significant yield increase in 1988-1991, while FPG-5 was n o t tested previously so its continuity could not be evaluated (Table 1). T h e r e were a few statistically significant changes, mostly negative, of lint percent, boll size, and seed index upon the various treatments (Table 1). T r e a t m e n t with Burst and PG-IV appeared t o elicit negative trends in yield, while the trends with Maxon were slightly positive.
J. Apic. Food Chem., Vol. 42, NO. 6, 1994 1957
Effects of Plant Growth Regulators on Cotton Table 2. Summary of Changes in the Allelochemicals of Cotton Squares (Buds) Treated with Selected Commercial Plant Growth Regulators and UreaM gossypol tannins flavonoids year cultivar compd low high low high low high 1986 ST-213 Burst +9.5 +28.6* +16.6 +3.8 +2.7 -0.9 1988 DPLdO Burst -6.1 -4.1 +11.4 +8.8 +2.3 +0.5 av Burst +1.7 +12.3 +14.0 +6.3 +2.5 -0.2 1988 DPL-50 1989 DPL-50 1990 DPL-50 1990 DPL-50 1991 DES-119 1991 DPL-50 av
Triggrr -16.7* -24.5* +21.7 Triggrr 0.0 0.0 -4.5 Triggrr -5.4 +2.7 -4.4 Triggrr 0.0 0.0 -10.1 Triggrr 0.0 +29.7* +6.8 Triggrr +2.8 +8.3 Triggrr -3.2 +2.7 +1.9
+19.0 +2.7 -10.8 -2.1 +1.9
-18.9 -3.2 +5.1 -8.3 -5.4 +1.7 +1.9 -4.8
-27.6 -2.3 +7.1 -6.9 -8.1 +1.1
-3.8
0.0 +3.0 +5.4 +8.7 +2.0 +3.0 1990 DPL-50 PG-IV 1991 DPL-50 PG-IV -16.2* +10.8* -29.0 -33.3 +1.7 +1.1 1991 DES-119 PG-IV +6.3 +3.1 +8.2 +1.5 +5.6 -11.8 -12.3 +4.0 +1.9 PG-IV -3.3 av
1990 DPLdO Maxon -16.2* 1990 DPLdO Maxon +3.0 av Maxon -6.6 1989 DPL-50 1990 DPL-50 1990 DPL-50 1991 DPL-50 1991 DES-119 av
urea urea urea urea urea urea
+2.7 -3.4 -8.5 +8.6 +7.6 +6.1* -16.2 -20.3 +4.1 +1.8 -9.8 -14.4 +6.4 +4.7 +4.4
-0.5 +1.4 +3.3 -3.3 +2.3 -4.5 -1.5 -6.0 0.0 -1.9 -3.4 +4.9 +10.8* +8.1* +3.4 +13.9 -4.3 -4.3 +1.7 +0.6 -1.6 +2.6
-5.1 -2.8 -1.0 +1.5 -4.6 +4.6 -6.0 -3.7 -4.2 +1.5
* The average contents during the study period of controls were as follows: gossypol,0.32%;tannins,11.99%;flavonoids,1.78%.*See Table 1 for rates and numbers of applications. Percent change of gossypol, tannins, and flavonoids from the specific control that accompaniedthe test; values marked with an asterisk were statistically significant. With regard to allelochemicals,positive trends in square gossypol were noted in some tests, particularly at the high rate, for Burst, Triggrr, and PG-IV (Table 2). Differences in responses to cultivars were not evident. Effects of the bioregulators on tannins and flavonoids were mixed, tending to be slightly increased. These results indicate that these bioregulators have only a limited positive effect on allelochemicals-secondary compounds-and presumably their indirect effect on insects is marginal. Other bioregulatorshave been reported to have asignificant effect on insects, however (Hedin, 1990). Urea was evaluated to determine if it had a positive effect on yield because it was known to be used as a foliar application in the nursery trade and reputedly has also been used as a foliar application to counteract stress in growing cotton. Typically, leaf color darkens in intensity when urea is applied. However, in our tests that were conducted over a 3-year period (Table 11,yield was actually decreased by 4.7 and 7.3% at the low and high levels (see rates in Table l ) , respectively. In one test, nearly 400 g h a - l ( l 0 times the low level) was applied over the season, resulting in about a 10% decrease in yield. In previous years, kinetin appeared to induce positive trends in yields of cotton, though not statistically significant (Hedin and McCarty, 1991). Of the present commercial bioregulators tested that were stated to contain cytokinins,Triggrr,FPG-5,andMaxon, allshowed positive yield trends in 1992 tests only, while Burst appeared to cause a negative trend. However, the changes were statistically significant in only two instances. The inclusion of IAA and GA in the FPG-5 formulation gave no
noticeable improvement over the commercial cytokinin formulations. The PG-IV formulation that contained IBA and GA, but not cytokinins, appeared to cause slightly negative trends. Finally,the two formulationscontaining inorganic micronutrients (FPG-5 and PG-IV) did not appear to be superior for yield over those that did not. ACKNOWLEDGMENT
We thank M. Petty, R. McPherson, and R. Hayes for technical assistance. LITERATURE CITED Elliott, M. C. The Regulation of Plant Growth. In Plant Growth Regulator Potential and Practice; Thomas, T. H., Ed.; BCPC Publications: London, 1982; pp 57-98. Guinn, G. Hormonal Relations During Reproduction. In Cotton
Physiology, Number One, The Cotton Foundation Reference Book Series;Mauney,J. R., McD. Stewart, J., Eds.; The Cotton Foundation: Memphis, TN, 1986; pp 113-136. Hedin, P. A. Bioregulator-Induced Changes in Allelochemicals and Their Effects on Plant Resistance to Pests. Crit. Rev. Plant Sci. 1990, 9, 371-379. Hedin, P.A.; McCarty, J. C., Jr. Effects of Kinetin Formulations on Allelochemicals and Agronomic Traits of Cotton. J.Agric. Food Chem. 1991,39, 549-553. Hedin, P. A.; Jenkins, J. N.; McCarty, J. C., Jr.; Mulrooney, J. E.; Parrott, W. L.; Borazjani, A,; Graves, C. H., Jr.; Fuller, T. H. Effects of 1,l-DimethylpiperdiniumChloride on the Pests and Allelochemicals of Cotton and Pecan. In Bioregulators: Chemistry and Uses; Ory,R. L. Rittig, F. R., Eds.; ACS Symposium Series 257; American Chemical Society: Washington, DC, 1984; pp 171-191. Hedin, P. A.; Jenkins, J. N.; Thompson, A. C.; McCarty, J. C., Jr.; Smith, D. H.; Parrott, W. L.; Shepherd, R. L. Effects of Bioregulators on Flavonoids, Insect Resistance, and Yield of Seed Cotton. J . Agric. Food Chem. 1988a, 36,1055-1061. Hedin, P. A,; McCarty, J. C., Jr.; Jenkins, J. N. Effects of CCC and PIX Related Bioregulators on Gossypol, Protein, Yield and Seed Properties of Cotton. J.Miss. Acad. Sci. 1988b, 33, 49-57. McCarty, J. C., Jr.; Hedin, P. A. Effects of Bioregulators on Allelochemicals, Proteins, and Agronomic Traits of Cotton. Miss. Agric. For. Exp. Stn. Res. Rep. 1989, 14, 1-5. McCarty, J. C., Jr.; Jenkins, J. N.; Hedin, P. A.; Shepherd, R. L.; Parrott, W. L. The Effects of Plant Growth Regulators on Cotton Yield in Two Environments. Miss. Agric. For. Exp. Stn. Res. Rep. 1987,12, 1-4. Miller, C. 0.;Skoog, F.; von Saltza, M. H.; Strong, F. M. Kinetin, a Cell Division Factor from Deoxyribonucleic Acid. J. Ana. Chem. SOC.1965, 77, 1392. SAS. User’s Guide: Statistics, version 5 ed.; SASInstitute: Cary, NC, 1985; 956 pp. Taiz, L.; Zeiger, E. Cytokinins. In Plant Physiology; Taiz, L., Zeiger, E., Eds.; Benjamin/Cummings Publishing: Redwood City, CA, 1991; pp 452-472. Weaver, R. J. Plant Growth Substances in Agriculture; Freeman: San Francisco, 1972; pp 99-103. Recieved for review September 16, 1993. Revised manuscript received January 3,1994. Accepted March 21,1994.. Mention of a trademark, proprietary product, or vendor does not constitute a guarantee or warranty of the product by the US.Department of Agriculture and does not imply its approval to the exclusion of other products or vendors that may also be suitable.
Abstract published in Advance A C S Abstracts, May 1, 1994.
